This invention relates to piston engines and more particularly to piston cooling oil systems wherein oil is sprayed into the pistons from a crankcase mounted windage tray having internal oil delivery passages.
It is known in the engine art to provide piston cooling oil sprayed against the inside of the individual pistons of an engine to cool the pistons to obtain higher engine power output or increased piston life. Such systems have been commonly used on many models of diesel engines but have generally not been used in automotive gasoline powered engines. However, in high output gasoline engines and for other engines for the purpose of increased emission control, the possibility of further extension of piston cooling in spark ignition engines has been considered.
Conventionally, piston cooling systems have operated with piston cooling nozzles through which oil is continuously applied in a stream or a spray on the piston interiors. The provision of such a system generally requires internal engine modifications and equipment which make difficult its application to engines previously manufactured. In addition, the continuous delivery of oil for cooling requires increased oil pumping capacity which uses energy and thereby reduces engine efficiency. A system in which these problems may be reduced or overcome is accordingly desired.
The present invention provides a piston cooling system for an engine which may be relatively easily adapted to engines in current production as well as to new engine designs. The system modifies the windage tray, commonly used in engines to reduce oil aeration, to provide an assembly through which piston cooling oil may be delivered to the underside of the engine pistons.
Instead of a single stamped sheet, the windage tray may be made from a pair of sheets, of metal or a suitable non-metallic material, which are welded or bonded together to form an assembly. One or both sheets are embossed so as to provide internal oil passages between the sheets that are used to transport oil from individual inlet openings to outlet openings provided with nozzles for directing cooling oil to each of the pistons individually.
In a preferred embodiment, the windage tray assembly is mounted to lower ends of the crankshaft bearing caps that support the engine crankshaft. The bearing caps include oil passages that carry oil from the pressure lubricated bearings supporting the crankshaft to outlet connections that feed oil to the inlet openings in the windage tray. The internal passages in the tray carry the oil from the inlet openings to outlet openings positioned on the tray so as to direct oil through the nozzles toward the interiors of the respective pistons. The arrangement utilizes the windage tray and bearing caps as carriers for piston cooling oil obtained from the bearing caps which are already supplied with oil for lubricating the bearings. Thus, modifications of the engine required to install a piston cooling system are limited to redesign of the windage tray to a sandwich-like assembly with oil passages and modification of the bearing caps to conduct oil from the bearings to the windage tray passages.
In order to reduce the energy expended in pumping the piston cooling oil, the engine bearing caps and the bearings therein may be modified to connect with oil feed holes in the associated crankshaft bearing journals so that oil distribution holes in the bearing caps connect intermittently with the crankshaft journal feed passages. Thus, oil is distributed in individually timed streams or sprays directed toward the pistons for a short interval once every revolution of the engine crankshaft. In this way, the amount of cooling oil utilized is limited and the energy expended in pumping the cooling oil is reduced, allowing for increased efficiency of the engine.